virtualbox I/O 3 times slower than KVM?

[typo W]

Hi, I'm brand new to virtualbox, so pardon me in case I made stupid mistakes.  I created a FreeBSD guest out of the regular virtualbox port (3.2.12) on FreeBSD 8.2, then timed the copying of a 320MB binary file to another file, which took 4 seconds, ie, 80MB/s.  On an identical hardware I created a CentOS guest out of KVM running on CentOS, and the same operation only takes 1 second.  On both hosts, the copy takes 1 second.  That is, virtualbox slowed the copying to 1/4 speed on my guest FreeBSD.

Both hosts are Dell R710, with 6 x 600GB 15K SAS drives forming a RAID6 with R700 controller with 512MB cache.

I'm testing in preparation of production servers, so would prefer regular ports, ie, 4.0.6 tar ball is out of question for now.